Caballero ($39.95, paper $19.95; June 3, 1996; 350 pp.; 0-89096- 701-6; paper 0-89096-700-8). Written in the 1930s and '40s, recently rediscovered and now published for the first time, this appealing saga traces the aftereffects on a once-prosperous Mexican family of the US annexation (in the mid19th century) of the southern Texas territory in which they have long lived. Gonz†lez, who was a well-known folklorist and teacher, and her collaborator (of whom virtually nothing is known) paint a knowledgeable picture of the subsequent Mexican War and of lives irrevocably changed by it. But a strong undercurrent of romantic clichÇs makes what might have been a Mexican American Gone With the Wind an only mediocre fiction that's of primarily sociological interest.